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Table 3 Factors associated with increasing lytA cycle threshold value (Ct-value) among lytA-positive patients hospitalized with severe acute respiratory illness at Chris Hani-Baragwanath Academic Hospital, Soweto, South Africa, 2009–2012

From: Assessing the impact of pneumococcal conjugate vaccines on invasive pneumococcal disease using polymerase chain reaction-based surveillance: an experience from South Africa

Variable lytA Ct-value Proportional-Odds Model
Univariate analysis Multivariable analysis
Total
n (%)
≤30
n (%)
31-34
n (%)
≥35
n (%)
ORb
(95 % CI)
p-value aORb
(95 % CI)
p-value
Age (in years) N = 603 N = 71 N = 128 N = 404     
 <2 125 (20.7) 6 (8.5) 11 (8.6) 108 (26.7) Reference -   
 2–4 24 (4.0) 0 (0.0) 6 (4.7) 18 (4.5) 0.5 (0.2-1.5) 0.227   
 5–24 44 (7.3) 2 (2.8) 13 (10.2) 29 (7.2) 0.3 (0.2-0.7) 0.008   
 25–44 268 (44.4) 48 (67.6) 59 (46.1) 161 (39.8) 0.2 (0.1-0.4) <0.001   
 45–64 135 (22.4) 14 (19.7) 37 (28.9) 84 (20.8) 0.3 (0.1-0.5) <0.001   
 ≥65 7 (1.2) 1 (1.4) 2 (1.5) 4 (1.0) 0.2 (0.1-1.1) <0.051   
Sex N = 603 N = 71 N = 128 N = 404     
 Male 257 (42.6) 27 (38.0) 64 (50.0) 166 (41.1) Reference -   
 Female 346 (57.4) 44 (62.0) 64 (50.0) 238 (58.9) 1.1 0.453   
Year N = 607 N = 71 N = 129 N = 407     
 2009 129 (21.3) 8 (11.3) 18 (13.9) 103 (25.3) Reference -   
 2010 173 (28.5) 34 (47.9) 46 (35.7) 93 (22.8) 0.3 (0.2–0.5) <0.001   
 2011 150 (24.7) 10 (14.1) 39 (30.2) 101 (24.8) 0.6 (0.3–0.9) 0.033   
 2012 155 (25.5 19 (26.8) 26 (20.2) 110 (27.0) 0.6 (0.3–1.1) 0.064   
Extraction Instrument N = 607 N = 71 N = 129 N = 407     
 Roche MagNA Pure LC 1.0 136 (22.4) 9 (12.7) 19 (14.7) 108 (26.5) Reference - Reference -
 Roche MagNA Pure LC 2.0 400 (65.9) 54 (76.1) 96 (74.4) 250 (61.4) 0.4 (0.3–0.7) <0.001 0.4 (0.2–0.6) <0.001
 Roche MagNA Pure 96 71 (11.7) 8 (11.3) 14 (10.8) 49 (12.0) 0.6 (0.3–1.1) 0.092 0.3 (0.1–0.7) 0.004
Antibiotics 24H before admission N = 601 N = 71 N = 128 N = 402     
 No 567 (94.3) 68 (95.8) 122 (95.3) 377 (93.8) Reference -   
 Yes 34 (5.7) 3 (4.2) 6 (4.7) 25 (6.2) 1.4 (0.6–3.0) 0.393   
Antibiotics during admission N = 586 N = 69 N = 126 N = 391     
 No 19 (3.2) 3 (4.3) 2 (1.6) 14 (3.6) Reference -   
 Yes 567 (96.8) 66 (95.6) 124 (98.4) 377 (96.4) 0.8 (0.3–2.2) 0.647   
Underlying medical conditionsa N = 603 N = 71 N = 128 N = 404     
 No 565 (93.7) 66 (93.0) 120 (93.7) 379 (93.8) Reference -   
 Yes 38 (6.3) 5 (7.0) 8 (6.3) 25 (6.2) 0.9 (0.5–1.8) 0.839   
HIV infection N = 558 N = 66 N = 119 N = 373     
 No 163 (29.2) 5 (7.6) 22 (18.5) 136 (36.5) Reference - Reference -
 Yes 395 (70.8) 61 (92.4) 97 (81.5) 237 (63.5) 0.3 (0.2–0.5) <0.001 0.4 (0.2–0.7) 0.001
PCV serotypes/serogroups N = 607 N = 71 N = 129 N = 407     
 PCV-7 111 (18.3) 13 (18.3) 28 (21.7) 70 (17.2) Reference - Reference -
 PCV-13 138 (22.7) 35 (49.3) 62 (48.1) 41 (10.1) 0.3 (0.2–0.5) <0.001 0.3 (0.2–0.5) <0.001
 NVT 358 (59.0) 23 (32.4) 39 (30.2) 296 (72.7) 2.7 (1.7–4.4) <0.001 2.7 (1.6–4.6) <0.001
Duration of symptoms (in days) N = 602 N = 71 N = 127 N = 404     
 0–2 204 (33.9) 14 (19.7) 38 (29.9) 152 (37.6) Reference -   
 ≥3 398 (66.1) 57 (80.3) 89 (70.1) 252 (62.4) 0.6 (0.4–0.8) 0.003   
Duration of hospitalization (in days) N = 602 N = 71 N = 129 N = 402     
 0–2 92 (15.3) 1 (1.4) 15 (11.6) 76 918.9) Reference - Reference -
 3–7 267 (44.3) 26 (36.6) 61 (47.3) 180 (44.8) 0.4 (0.2–0.8) 0.004 0.5 (0.2–1.1) 0.071
 ≥8 243 (40.4) 44 (62.0) 53 (41.1) 146 (36.3) 0.3 (0.1–0.5) <0.001 0.3 (0.1–0.6) 0.002
In-hospital outcome N = 603 N = 71 N = 129 N = 403     
 Survived 562 (93.2) 58 (81.7) 119 (92.2) 385 (95.5) Reference - Reference -
 Died 41 (6.8) 13 (18.31) 10 (7.8) 18 (4.5) 0.3 (0.2–0.6) <0.001 0.3 (0.2–0.7) 0.003
  1. Abbreviations: OR: odds ratio; aOR: adjusted odds ratio; CI: confidence interval; HIV: human immunideficency virus; PCV-7: 7-valent pneumococcal conjugate vaccine serotypes (included serotypes/serogroups 4, 6A/B, 9A/V/L/N, 14, 18A/B/C, 19B/F, 23 F); PCV-13: additional 13-valent pneumococcal conjugate vaccineserotypes (included serotypes/serogroups 1, 3, 5, 7A/F, 19A); NVT: serotypes/serogroups not included in PCV-7 or PCV-13, including samples that tested negative for the 42 serotypes detected by the serotyping assay
  2. a Underlying medical conditions included: asthma, chronic lung disease, chronic heart disease, liver disease, renal disease, diabetes mellitus, immunocompromizing conditions excluding HIV infection or neurological disease
  3. b The odds ratio of the proportional-odds model measures the effect of a predictor on the odds of being above a specified level, compared with the odds of being at or below the specified level